The invention relates to an apparatus for severing the vent of slaughtered poultry, comprising positing and stretching means for the poultry, a centring pin having a thickened end portion to be inserted into the vent and being movable in relation to the positing and stretching means, a clamping sleeve concentrically surrounding and being movable in relation to the cenetring pin for clamping the orbicular muscle surrounding the vent between same clamping sleeve and the centring pin, and a shell-shaped rotary cutter concentrically surrounding the centring pin and clamping sleeve for severing the vent.
With the known apparatuses of this kind (which are usually but not solely equipped to process poultry while the same is suspended from an overhead conveyor), the positioning and stretching means consist substantially of one of a number of stretching brackets that engage the lower body of the poultry between or near the legs. After the poultry has been fixed with the aid of said positioning and stretching means, the centering pin with its thickened end portion is inserted into the vent. With the aid of the rotary cutter the skin is then cut around the vent after which by a relative displacement of the centring pin in relation to the clamping sleeve, the cut vent and the orbicular muscle are clamped between the clamping sleeve and the head of the centering pin. In this manner the vent and the intestines connected thereto are drawn at least partially from the poultry.
Although with this prior art apparatus there is a relative longitudinal displacement of the centering pin in relation to the clamping sleeve and the cutter, these parts of the prior art apparatus nevertheless have a fixed rotational position in relation to one another. This means that the centering pin and the clamping sleeve rotate together with the shell-shaped rotary cutter.
This known apparatus has several disadvantages. Practice has shown that the positioning and stretching means used can not always optimally guarantee that the skin surrounding the vent is pulled sufficiently tight. Consequently, it is not always possible to obtain an optimal cut (i.e. a small hole around the orbicular muscle). In some cases it is therefore necessary for the cutter to be inserted deeper into the slaughtered poultry, involving the risk of undesirable intestinal damage (whereby the intestinal contents render the meat unsuitable for consumption due to contamination). Similarly it may be necessary, if the cut made by the cutter is not complete, to partially tear the vent from the remaining part of the poultry, involving the risk of the intestine tearing.
Another disadvantage of the known apparatus arises from the fact that the centering pin and clamping sleeve rotate together with the cutter. This causes the intestine to become twisted with the possibility of the intestine tearing.
It is an object of the invention to provide an apparatus of the present type with which the above-mentioned disadvantages of prior art vent cutters are eliminated in a simple yet effective manner. Additional objects and advantages of the invention will be set forth in the following description, or may be obvious from the description or may be learned through practice of the invention.
To this end, the apparatus according to the invention is characterized in that the positioning and stretching means comprise a stretching sleeve that engages around the vent of the poultry and that is positioned such that the centering pin, the clamping sleeve and the cutter can move concentrically through the same, and that the centering pin and the clamping sleeve have a fixed rotational position.
It has been shown that with the aid of such a stretching sleeve, the skin surrounding the vent can be stretched optimally while at the same time preventing the skin from rotating with the cutter. In this way the shell-shaped cutter can make an optimal cut without the cut having to be inserted deeply into the poultry. This effectively prevents damage to the intestines. The fact that the centering pin and the clamping sleeve no longer rotate with the shell-shaped cutter but remain in a fixed position, also plays a role. Only the mutual longitudinal movement between the centering pin on the one hand and the clamping sleeve and the shell-shaped cutter on the other hand is possible.
By choosing a suitable shape for the stretching sleeve, it is possible to ensure that the same will make optimal contact with poultry having a very slack abdominal skin. Practice has shown that this makes the apparatus suitable for the best possible manner of processing poultry whose live weight comes within a greater range, for example, when the apparatus is set at 1500 to 2500 grams as opposed to 1800 to 2200 grams in the case of the known apparatus of this type.
In a preferred embodiment of the apparatus according to the invention, the cutter has a smooth cutting edge and a high rotational speed.
In the prior art apparatus the cutter has a low rotational speed (for example, 150 revolutions per minute) and the cutting edge is serrated. The combination of a low rotational speed and a serrated cutting-edge results in tearing the vent, ensuing in an irregular cut and possible intestinal damage. However, providing the cutter with a smooth edge and rotating it at high speed, results in a smooth cutting edge and minimizes the risk of intestinal damage. The prior art apparatus was not capable of a high rotational speed because the centering pin and the clamping sleeve rotated together with the shell-shaped cutter, and because a high rotational speed would result in unacceptable twisting of the intestine. However, as in accordance with the invention the centering pin and the clamping sleeve do not rotate, the cutter may have a high rotational speed without thereby causing the intestine to become twisted.
Within this framework it is preferred for the cutter to make at least 1000 revolutions per minute.
As already briefly mentioned in the above, the shape of the stretching sleeve is designed such as to allow optimal operation. For example, in a special variant of the apparatus according to the invention, the stretching sleeve is at the side that during use faces the tailbones of the poultry, preferably provided with a bevel. This ensures that this side also is properly in contact with the poultry.